Type font changing mechanism and controls

ABSTRACT

Type font changing in a teleprinter having a type font supporting carriage which positions the font unit along a writing line is facilitated by employing carriage movement in one direction to remove the presently installed type font unit from its character selection driving member and place it in a storage receptacle, and carriage movement in the opposite direction to retrieve a different font unit from a stored position and install it on the driving member. Manual and electrical controls are provided. Font units can be changed automatically in response to a single coded signal defining the desired font unit. Automatic tabular position memory is provided to record the carriage position at the time of initiation of font unit change so that after font unit removal and change the carriage can be automatically returned to the original position along the writing line and printing resumed.

United States Patent [1 1 Willcox 1 1 TYPE FONT CHANGING MECHANISM ANDCONTROLS Frederick P. Willcox, 565 Oenoke Ridge, New Canaan, Conn. 06840[22] Filed: Apr. 3, 1973 [21] Appl. No.: 347,456

[76] Inventor:

{52] U.S. Cl. ..197/18;197/53; 101/9318 [51] Int. Cl B41] 23/04 {58]Field of Search 197/16, 18, 19, 48, 52,

[56] References Cited UNITED STATES PATENTS 2,830,820 4/1958 Murchison276/2 3,291,292 12/1966 Netznik et a1, 199/18 X 3,307,672 3/1967Young 1. 197/18 X 3,334,721 8/1967 Hickerson 197/50 3,403.386 9/1968Perkins et a1..,. 340/1715 3,534,847 10/1970 Willcox i i 197/183,645,372 2/1972 Noell et a1. 197/18 3,657,627 4/1972 lnaba et a1.318/601 3,731,778 5/1973 Willcox 197/18 X a mw PRlNTER CONTROLS POWERSUPPLY INPUTS 1 July 1,1975

Primary Examiner-Edgar S. Burr Assistanz Examiner-R. T. Rader [57ABSTRACT Type font changing in a teleprinter having a type fontsupporting carriage which positions the font unit along a writing lineis facilitated by employing carriage movement in one direction to removethe presently installed type font unit from its character selectiondriving member and place it in a storage receptacle, and carriagemovement in the opposite direction to retrieve a different font unitfrom a stored position and install it on the driving member.

Manual and electrical controls are provided, Font units can be changedautomatically in response to a single coded signal defining the desiredfont unit. Automatic tabular position memory is provided to record thecarriage position at the time of initiation of font unit change so thatafter font unit removal and change the carriage can be automaticallyreturned to the original position along the writing line and printingresumed.

11 Claims, 8 Drawing Figures ATENTH 1 SHEET EAIJLI IIIIE 3.892.303

SHEET KEYBOARD r m EXTERNAL CODED SIGNAL SYSTEM PowER m INPuT SOURCESSUPPLY 0 INPuT 14* coNTRoL REEI J I! INPUT (c CHARACTER SHAFTENCODER./264 coNNANII SELECTION F REeIsTE CONTROL FONT MOTOR DUMPAI 25sTART IC=P i 270 OR @262 PRINT PRINTING NON- A I CONTROL DRIVE PRINTING AFUNCTION f 290 DECODER m PRINT a INHIBIT sNITcHER I 278 AND, 289 [K292 ICARRIAGE LINE POSITION FEED MEMORY CONTROLS UP uowN LETTER &DIll I:/E272 STD/PA, SPACE R Y PRINT COMMUTATOR CARRIAGE 31* CONTROLS R MQTORFONT ,-2so k L SELECTION E SW 29 sET-uP .A HI l LIMIT A sNITcN MEMORY282 TD N296 123L156 CODE /-284 ,sTow

GENERATOR FONT FONT SELECTION N- TAN TRANSFER 298 A CONTROL 5mm CONTROL& DRIVE & DRIVE "i-"-" INIII I975 5.892303 SHEET 4 352 KEYBOARD i /-354340 I EXTERNAL i c0051) SIGNAL QE'Q EQ INPuT SOURCES INPUT 1 1 19.8CONTROL -RESET (R) ,-as4 mm c CHARACTER COMMAND SELECTION SHAFT REGISTERCONTROL FONT MOTOR 35s TART" :=P 368 J 370 NO J 1 I PRINT PRINTINGPRINTING 0R CONTROL DRIVE ./"360 k M 390 DECODER BT51 PRINT INHIBITSWITCHER -R ANDMBZ 3R07 N V I Row 8 COUNTER (3) CHANGE 396 I 404 WRITE 14 RSEEN S-IRECORDING 406/ERASE 2 HEAD RECORDING 378 5-2 SWITCH HEAD LINE\R FEED R l 3 54 CONTROLS 1404 a DIIIVE r m LIMIT R m sNITcN MASRGIRN386 3T0P II 675 a PRINT TAB INNIBIT CARRIAGE COMMUTATOR [RUN ouTPOSITIONING CARRIAGE W CONTROLS MOTOR Q J) rLETTER SPACE \374 TYPE FONTCHANGING MECHANISM AND CONTROLS CROSS-REFERENCES TO RELATED APPLICATIONSThe following U.S. Patents and patent applications are referencedherein:

A. U.S. Pat. No. 3,461,235, Aug. 8, 1969, Willcox et al., DataTransmission System and Printer,

U.S. Pat. No. 3,534,847, Oct. 10, l970, Willcox,

High Speed Teleprinter;

C. Application Ser. No. 54,876, filed July I5, 1970, Willcox, forPrinter Having Individual Chips, now U.S. Pat. No. 3,731,778;

D. Application Ser. No. 69,104, filed Sept. 2, 1970,

Willcox, for Printer Format Controls.

BAC KGROUN D The prior art contains many examples of machines andmechanisms for changing work pieces. In the printing art,interchangeable type font magazines are employed in type castingmachines. Various methods of font shifting are used in photo-composingmachines. Typewriters and printers have been patented which employmultiple typeface-bearing elements generally mounted on a carrousel withdifferential drive. Recent art in the typewriter field showsmechanically complex, externally mounted means for changing and storingsingle type font elements. Type font element or unit changing, asapplied to typewriters and teleprinters is quite closely akin toautomatic tool changing as employed in computer controlled machinetools.

Inasmuch as most single element typewriters employ a carriage to supportthe single type font unit and posi tion it along the writing line, themovement of this carriage is used in this invention to effect font unitremoval, installation after changing and, in one structure, to effectstoring and retrieval from storing. By doing this the mechanicalstructure required has been greatly simplified and can be totallyenclosed in the normal confines of the printer case.

Code-signal control of the font changing is essential to maintainingmaximum machine speed. This invention provides this and also provides acontrol structure for the complex font changing operation that requiresonly one input signal which defines the stored location of the type fontelement that is wanted. Inasmuch as the font units are stored inrespective locations, this defining of the stored unit thus defines thefont unit itself.

The addition of a temporary tabular memory to record the position of thecarriage at the time of initiating font exchange and the associatedcontrols to effect carriage return to the recorded position afterexchanging is a novel feature of the invention and also aids inincreasing the throughput of the machine. It, too, is shown coupled intothe over-all code-controlled system. Prior art in the tabular structurefield is not generally applicable for such temporary use. There is oneexception, however, and this is incorporated herein by reference.

The following U.S. Patents are considered the closest prior art to thisinvention:

U.S. Pat. No. 3,645,372, Feb. 2, 1972 Noel] et al., which is to anautomatic font changing apparatus and which cites patents:

U.S. Pat. No 3,417,379 Dec. 12,1968 Heard et al.,

and

2 U.S. Pat. No. 3,404,766, Oct. 10, l968 Castle et al.

U.S. Pat. No. 3,613,224, Oct. 10, 1971 Newton et al, and U.S. Pat. No.3,657,627, Apr. 4, I972, Inaba et al., which are typical referencesshowing automatic tool changing in machine tools;

U.S. Pat. No. 3,554,347, Jan. 1, 1971, Perkins, showing a magneticmemory in relation to carriage travel;

U.S. Pat. No. 2,971,626, Feb. 2, 1961, Dirks, showing a drum magneticmemory in a typewriter which is used in relation to justification;

U.S. Pat. No. 3,434,768, Dec. 12, I969, Willcox et al., incrementalmagnetic buffer storage;

U.S. Pat. No. 3,403,386, Sept. 9, 1968, Perkins et al.,

format control;

FIG. I is an isometric view of a printer mechanism incorporatingautomatic font unit changing and storage;

FIG. 2 is a partial front view of a vertically mounted type font unitshowing method of type font removal and storage;

FIG. 3 is a partial top view of FIG. 2',

FIG. 4 is a side view of a printer incorporating a type font unitchanging mechanism and an internally located storage drum;

FIG. 5 shows a top view of the storage drum and a portion of thechanging mechanism;

FIG. 6 shows a top view of a sliding storage box and a portion of thefont changing mechanism and also shows power positioning devices forfont changing and selecting.

FIG. 7 is a block diagram of a printer incorporating font unit changing,carriage position memory, and code-signal-responsive controls; and

FIG. 8 is a block diagram similar to FIG. 7 incorporating the type ofcarriage position memory shown in FIG. 1.

DESCRIPTION OF THE INVENTION FIGS. 1 to 6 incorporate a type font unitor element of the type shown in detail in Cross-Ref. C. This type fontunit has a plurality of type-face bearing chips which are stowed in adrum. Any one of the chips may be selected, extracted, used to printwith, and then restowed in the drum.

The type font unit shown and described in Cross-Ref. B could easily besubstituted in the mechanisms shown in FIGS. 1, 4, 5, and 6. This fontunit is spool-shaped and has the type faces located on the ends of smallarms which are stowed parallel to the spool axis. The selected arm, andtype face, is swung out from its stored position, and, after printing isswung back to storage.

In either referenced structure, the type font unit is removable from thecharacter selection driving means and readily replaceable with adifferent font unit having a different type style, size, or charactermake-up. Both references also show various means of supporting the frontunit and its positioning along the writing line by a carriage orcarrier.

The type font unit supporting structure and method of removal as shownin FIGS. 2 and 3 can be readily applied to type font unit structures ofthe unitary element variety such as spherical-surfaced or cylindricalsurfaced one-piece moldings which have a plurality of type faces on thesurface thereof.

FIG. 1 shows the basic elements of a serial printer incorporating asimple type font unit changing mechanism and the basic controls forautomatic code-signalresponsive operation. A type front drum 10 isslidably supported or mounted on a drive member or shaft 12 and isrotatably positioned on a selected character by a front drive [4.Character to is effected by printer controls l6 in response to an inputcommand. The character selection part of controls 16 compares the inputsignal with the present font position signal received from shaftposition encoder 18 which is mounted on font drive 14. Controls 16 areconnected to certain elements of the printer including drive 14 andencoder 18 by a cable means generally designated 17.

When character selection has been completed, chip ejector magnet 20 isactuated by controls 16 over leads 21 pushing a type-face bearing chip,(not shown), into printing arm 22. Arm 22 is then rotated to printingposition as indicated by the dotted line position 24 by print actuator26 which is also energised by controls 16 over leads 27. A recordingmaterial, such as a pressure sensitive paper, is indicated generally at28, and is supported by a platen or roller 30.

Font drum 10 is moved along shaft 12 by a carriage indicated generallyby 32. Carriage side plates 34 and 36 straddle drum l and respectivelysupport actuator 26 and magnet 20. A chip retaining disc 38 is fixed toside plate 34 and is cut away to clear arm 22. Shaft 12 is slidably androtatably journaled in a boss (not shown) on side plate 34. Suitablestructures for this dual bearing are shown in Cross-Refs. B and C. Sideplate 36 has an aperture which closely surrounds shaft 12 but does nottouch it.

Carriage 32 is slidably mounted on guide ways, (not shown), forpositioning along the writing line. A cable 40 is anchored to carriage32 and is wrapped around cable drum 42 and idler sheave 43. Cable drum42 is fastened on one end of motor shaft 44. Carriage motor 46incrementally positions carriage 32 and font drum along the writingline. Motor 46 has a feedback commutator 48. A belt pulley 50 isfastened on the other end of shaft 44.

A carriage tabular position memory, indicated generally by 52, comprisesa magnetic drum 54 and a magnetic write, read, erase, transducer head 56which is connected to controls 16, Drum 54 is connected to a belt pulley58 and is driven by belt 60 in synchronism with the positioning ofcarriage 32. The ratio of pulleys 50 and 58 is nominally selected togive almost one rev olution of the magnetic drum 54 for the maximumtravel distance of carriage 32. Belt 60 may be of the toothed timingvariety.

A type font unit transfer member or receiver is shown generally at 62and is mounted on shaft 64 for rotation about its axis. Receiver 62 isshown with four type font unit receiving positions. Inasmuch as receiver62 is somewhat skeletonized, the receiving positions are located at theends of respective arms 66, 68, 70, and 72. Arms 66, 68, and 70 areshown with type font units stowed or retained thereby. Four detentpositions are provided for receiver 62. A non-rotating guide plate 74,supported by the machine frame, is closely positioned to transfer memberor receiver 62 and to the faces of the spare font drums retained byreceiver 62 to keep the type chips from falling out of their respectivedrums when the receiver 62 is rotated to transfer a font drum from oneposition to the next.

Arm 72 is shown in position to receive drum 10 should the printeroperator decide to use a different font. Member 62 is held in receivingposition by the head end of shaft support 76. This support 76 isslidably journalled in a boss 78 on the machine frame and is urged intoengagement with the outboard end of shaft 12 by spring 79. The head endof support 76 encloses a bearing which, when engaged, journals a reduceddiameter projection on the end of shaft 12. It should be noted that theforked ends of arms 66-72 may be slightly resilient to aid in drumretention and, further, that the receiving positions in receiver 62could be apertures or cavities with each having a radial cut awayportion to permit the passage of carriage side plate 34.

Upon receipt of a font change signal, printer controls 16 effectsrotation of drum 10 to a character position which also represents theremoval alignment position of drum 10. This brings pin 80 on drum 10into alignment for entering hole 82 in arm 72. Printing with thischaracter chip which has been selected is inhibited by the font changesignal and, when drum 10 has been aligned or indexed to font changeposition, carriage motor 46 is energized by controls 16 and carriage 32moves toward the transfer member and receiver 62.

At the time carriage motor 46 is actuated to begin a font changeoperation, controls 16 sends a write signal pulse to transducer head 56to record the position of carriage 32 at the time font change wasinitiated. In actual practice, the write" pulse would be sent to head 56after one or two or more incremental positioning pulses had been sent tocarriage motor 46 so that after font unit change and the carriage isreturned to the recorded position, the recorded position would be readout" by head 56 in advance of the final stopping position to providetime for decelerating and stopping carriage 32.

As the carriage moves toward the receiver, side plate 36 engages shaftsupport 76 pushing it off the end of shaft 12 and out of the forked endof arm 72 so that hub 84 of drum 10 can enter the forked end of arm 72.A limit switch 86, supported by the machine frame to engage a portion ofcarriage 32 at its limit of travel, effects termination of carriagemotion by sending a signal to controls 16 over leads 87 when actuated bythe carriage.

When drum 10 is fully against arm 72 and pin 80 has entered hole 82, thedrum 10 is completely disengaged from shaft 12. Guard plate 74 is cutout at 88 so as to clear chip retaining disc 38 which, at the end ofcarriage travel or motion, comes into alignment with the guard plate. Itwill be noted that the external dimensions and configuration of sideplate 36 are such that the plate can freely pass through the forked endof arm 72.

At this point, with the carriage stopped at its limit of travel,transfer member or receiver 62 can be rotated by actuator 90 affixed toshaft 64 to transfer font drum 10 from its position between side plates34 and 36 and bring the next desired font unit or drum into position forinstallation on shaft 12. Actuator 90 may be nothing more than amanually operated knob or, as shown, a selection device actuated bycontrols 16 over leads 92 in response to an input signal calling for aspecific font unit or drum, generally identified by its location inreceiver 62. The spare font drums as indicated at 63, 65, and 67,previously placed in storage and retained by the arms of receiver 62,just clear guard plate 74 when the receiver is rotated.

When the specific, selected font drum has been brought into alignmentwith shaft 12, controls 16, in response to a font restore signal, againenergizes carriage motor 46 with a series of positioning pulses to movethe carriage away from its limit of travel and back toward the recordedposition previously described. As the carriage moves away from the limitstop, the newly selected font drum is slid out of the forked end of there spective receiver arm and onto shaft 12. As carriage 32 continuestravel support 76 follows side plate 36 until it has engaged the end ofshaft 12. Carriage 32 continues travel in this return, or font restore,direction until transducer head 56 reads out the previously recordedposition and thus effects stopping of motor 46 by controls 16. Thememory drum 54 is erased when the first following carriage returnoperation is executed. This erasure takes place automatically.

In the foregoing description the font selection drive 14 and carriagemotor 46 are assumed to be stepping motors. Obviously there are manypossible equivalents as shown, for example, in Cross-Ref. B. Carriagemovement, in one direction, can be spring-powered with suitable stoppingand detent means. Further, mechanical limit stops and interlocks can beused.

From the foregoing description of the structure shown in FIG. 1 it canbe seen that a. the font drum or element is transported from itsposition along the writing line and is removed from its driving meansand stored by one single motion;

b. the removed or old font drum is then transferred from its carriageconfinement and a new font drum is brought into installing position byanother single motion; and

c. the new font drum or element is installed on the driving meanssimultaneously with its extraction from its stowed position and istransported back to printing position by a final single motion in adirection reverse to the first motion.

FIGS. 2 and 3 illustrate the application of the same type of transfermember or receiver as shown in FIG. 1 but horizontally mounted so as toreceive and exchange font elements or drums that are supported on avertical axis. In FIG. 2 font drum 100 is retained on a short slidabledrive member 102 which is rotated through spiral gears by anoff-carriage font drive motors as shown in FIG. 1. Drive member 102passes through carriage 104 which is slidably mounted for movement andpositioning along the writing line. Carriage 104 also supports the chipejection and printing means, as shown for example in FIGS. 4 & 5 ofCross- Ref. C.

A font transfer and storage member on font receiver is generallyindicated at 106 and is mounted principally on a hollow tubular shaft108 journalled in support 110, and is rotated by knob 112. Member 106has four font drum storage arms which are generally like those ofreceiver 62, except that the ends of the arms are bifurcated by a longslot 114 as shown in FIG. 3 so as to be slightly springy to retain afont drum and, also, to guide the drum indexing or alignment pin 116.

When carriage 104 travels to the right, in FIG. 2, in response to a fontchange signal, the hub 118 of drum 100 starts to enter arm 120 of member106, drive shaft or member 102 is extracted from drum 100 by action ofbellcrank 122 which is pivoted on a pin projecting from a bracketextension of carriage 104. End 124, (generally forked), of bellcrank 122engages a circumferential groove 126 in the enlarged end of member 102and keeps member 102 in engagement with drum under the urging of spring128 bearing upon the upper end of bellcrank arm 130.

As carriage 104 moves to the right as indicated, the head on upper arm130 strikes spring plate 132, bellcrank 122 is rotated to the dottedline position and member 102 is moved downward to the dotted lineposition and out of engagement with drum 100. When carriage 104 hasreached the limit of its travel. knob 112 can be rotated to remove drum100 from its confinement on carriage 104 and to bring a new font drum orelement into installing position. Inasmuch as the springy ends of thearms of member 106 tend to retain the hub of the drum, it is necessaryfor member 102 to engage the hub of the newly selected drum beforecarriage return to the original position is initiated. This isaccomplished by pushing font restore button 134 on plunger 136. The endof plunger 136 presses spring plate 132 downward and thus releases thehead of bellcrank arm 130 so that spring 128, acting through thebellcrank, forces shaft or member 102 into the newly selected drum orfont element. A font restore switch 138 can be so positioned as to beactuated by the motion of plunger 136 so as to initiate carriage returnto the desired printing position. This desired printing position mayhave been previously recorded as a temporary tabulaion position asdescribed in relation to FIG. 1.

Drum 100 is shown as having similar construction to drum 10 of FIG. 1 tofacilitate illustration. In actual practice, a font drum for verticalsupport as in FIG. 2, may well be hub-less and the upper end of member102 may well be a disc, slightly larger in diameter than the hub shownand fitted with driving pins or the like. The disc would retract into acavity in the top of carriage 104. With either this method of drivingsupport, or that shown, the font drum 100, is held in its installedposition on the driving member by an overarm plate 105 which isessentially part of the carriage structure. The font drums are retainedin a similar manner in member 106 by fixed overarm plate 107.

FIG. 4 shows a side view of a printer similar to that previouslyillustrated but incorporating a separate and larger capacity fontstorage magazine or bin which is wholly contained within the normalconfines of the printer case.

The printer case is indicated generally by 140, and the keyboard isindicated at 142. A type font drum is confined by side plates 152 and154 of carriage 156 and is rotated for character selection or removalalignment by shaft 158. The chip ejection, printing, and restowingmechanism is similar to that shown in FIGS. 1 and 2 of Cross-Ref. C.Printing arm 160 accepts a type chip ejected from drum 150 by solenoid162 and is swung up into printing position as shown by the dotted lines.Impression paper is indicated at 164 and is supported by platen 166.

Carriage 156 is incrementally positioned along guide bar 168 by means ofa cable 170 which is looped or wound around cable drum 172 affixed onthe output shaft of carriage motor 174. A motor commutator or feedbackpulse generator is indicated at 176. A carriage travel limit switch isindicated at 178.

A bracket fixed to guide bar 168 supports a font drum receiver ortransfer arm 182 which is fixed to a shaft 184 pivoted in bracket 180.Arm 182 is normally 7 retained in its upper, or solid line position by aspringloaded shaft support such as support 76 in FIG. 1.

Arm 182 receives the font drum or element to be changed in exactly thesame manner as previously de scribed in relation to FIG. 1. However, inthis structure, arm 182 is used to transfer the font unit or drum to bechanged from confinement between carriage side plates 152 and 154 to afont bin or magazine 186. This magazine 186, shown in top view in FIG.5, has six font storage positions or cavities and is supported by shaft188 journalled in boss 190 and may be rotated by the font selecting knob192 which is adjacent the keyboard keys.

When the type font unit or drum 150 is to be changed, the same procedureas previously described for FIG. 1 may be used. The hub ofdrum 150enters the forked end of arm 182 and the drum index pin 194 enters slot196 in arm 182. A font retaining lever 198 is pivotted at 200 in a longslot that separates most of the length of arm 182 and is pulled into aspring-loaded position by spring 202. The upper end of lever 198 iscurved so as to press the font drum hub into the forked end of arm 182.As the drum hub enters the forked end of arm 182, lever 198 is rotatedslightly outward by the normally bevelled end of the drum hub.

To transfer the font drum thus received to magazine 186, arm 182 isrotated downward by a knob 204, shown in FIG. 5, and the font drum ispositioned in the empty storage cavity or receptacle of magazine 186where it is retained by the spring pressure of rim finger 206 which isnominally an integral part of the magazine structure as shown. As arm182 is further rotated to the dotted line position to clear themagazine, retaining lever is disengaged from the hub of the juststoredfont drum by the lower end of lever 198 riding up on cam surface 208which is part of bracket 180. Magazine 186 can now be rotated to bring aselected and desired font drum into position for transfer up to theinstallation position. Arm 182 is now rotated clockwise to pick up thenewly selected font drum and carry it up to confinement between sideplates 152 and 154. As arm 182 engages the hub of the drum to beinstalled, lever 198 leaves the active cam surface 208 and firmly forcesthe hub into the forked end of arm 182 so that it will be in exactposition for sliding on to shaft 158.

Font restoring, i.e., carriage return to printing position, is effectedas described in conjunction with FIG. 1. Obviously, the structure ofFIG. 4 can be fitted with the temporary carriage position recordingmeans also previously described. It should be noted that when arm 182 isin its upper position, the elbow of the arm 182 partially projects intothe empty storage cavity and keeps the magazine 186 from beinginadvertently rotated.

FIG. 5 shows a top view of magazine 186 and with arm 182 in the upwardor ready position. This figure shows the structural detail of themagazine which would normally be molded of a suitable plastic material.The cranked lower end of lever 198 is shown. Both arm 182 and lever 198have been sectioned through a point just above the pivot pin 200 asshown in solid lines in FIG. 4.

FIG. 6 shows an alternate front storage bin structure for the printer ofFIG. 4. In this case the magazine is a box-like structure 210 which canalso be contained within the normal confines of the printer case 140.Box 210 is slidably supported on guides 211 for to and fro positioningas indicated by the double ended arrow. Box 210 has a rack 212 on itsbackside which engages a gear 214 which is rotated by a pinion 216 onthe output shaft of font selector 218, which, in turn, is actuated bysignals from the printer controls over leads 220.

In FIG. 6 the drive shaft 184, which is connected to arm 182, is alsoconnected to a font unit transfer actuator 222, which is also connectedto printer controls by leads 224. Font selector 218 and actuator 222 maybe stepping motors, solenoids, or the like. Stored font units 226, 227,228, and 229 are shown in place in box 210.

In FIG. 4 a stored or stowed font unit 187 is shown in place in magazine186. In FIG. 5 this same font unit 187 is shown in the same relativelocation as in the side view of FIG. 4. Other spare font units areindicated at 189, 191, 193, and 195.

FIG. 7 is a block diagram of a code-signal-responsive electricallycontrolled printer incorporating automatic font unit changing, carriageposition memory, and font selection control. It shows the essentialdetails of complete control of printer structures such as shown in FIGS.1 to 6 and is applicable to other printer structures as well.

An input control 250 receives input command signal from either akeyboard 252 or external coded signal input sources 254. The externalsources 254 may be a computer, a tape reader, or a remote source whichsends its input command signals via radio or telephone links. The inputcontrol 250 may include a serial-toparallel converter and may control orsignal the external source. Methods of handling serial or parallel codedinput signals are shown, for example, in Cross-Ref. A.

Coded input signals, parallel by bit, are entered in command register256 and presented to character selection control 258, and tonon-printing function decoder 260. If the input command signal does notcall for a non-printing function, a not non-printing function signal WF,serves as a start signal, through OR gate 262, to energize selectioncontrol 258 which compares the command signal C with the present fontposition signal P from font drive shaft position encoder 264 which ismounted on the font drive motor 266. If the signals C and P are notequal, C P, the font motor 266 is energized to rotate the font unit orelement to the selected character. During the rotation or bringing thefont unit to the selected character, the signals C and P arecontinuously compared for equality. When C=P, motor 266 is stopped andprint control 268 is energized to effect printing of the selectedcharacter by printing drive 270. In the case of printing structuresshown in FIGS. 1 and 4, this involves a sequence of type chip ejection,transport to printing position, printing with the chip, and then chipreturn and re-stowing in the font drum.

At the completion of type chip-restowing, print control 268 puts out areset signal over one lead and a letter space signal over another lead.The letter space signal pulse initiates letter spacing by print carriagecontrols 272 which, in turn, effects carriage movement through carriagemotor 274. A feedback commutator 276 is connected to one output shaft ofmotor 274 to provide for accurate stepping of the motor.

If the input command signal is for a non-printing function involvingline feeding, line feed controls and drive 278 is energized to carry outthe command. If the input command signal is for a particular carriageoperation such as return, tabulating, spacing, etc., the carriagepositioning controls 272 is appropriately energized. Likewise, othernon-printing functions (not shown), such as bell, etc., would beappropriately effected.

A reset signal pulse is put out by line feed controls and drive 278 atthe completion of each operation such as line feed, vertical tabulating,and the like. Print carriage positioning controls 272 also puts out areset pulse after all operations which it effects except letter space.As previously described print control 268 puts out a reset pulse afterthe printing of a selected character. This is done so that the nextcommand can be entered into register 256 and selection initiated duringthe completion of letter spacing, i.e., some overlap is permitted. toavoid possible interference such as would occur when a repeat characteris selected, print control 268 incorporates a time delay circuit whichholds off acting on a C=P signal until the end of the delay period toinsure that letter spacing has indeed taken place. Other types ofinterlock circuits can, of course, be used. Regardless of the source ofthe reset pulse, designated R in the diagram, all the various functionalelements of the system that require resetting so as to be ready for thenext command are connected to receive this reset pulse. This same pulsecan be reflected back to the input sources to indicate a readycondition.

If the input command signal is a non-printing function signal callingfor a type font unit change by designating the font unit to be selected,or more properly its respective location in the storage magazine, thedecoded command for a specific font unit location in storage is sentover a respective lead from function decoder 260 to a font selectionset-up unit generally designated 280. This unit contains a limitedmemory 282 which may be a small group of flip-flops, a code generator284 which may be no more than a single-shot followed by a limited arrayof diodes, and certain control circuits for putting out signal pulses.

When the specific font unit location signal, such as might designate oneof six possible locations of font unit storage in the magazine, isreceived by the set-up unit 280, the appropriate memory cell latches up.Following this set-up unit 280 puts out a dump signal to reset register256 and remove the command. Following this dump signal by a brief delayto insure resetting of register 256, code generator 284 puts out aparallel-by bit coded signal to register 256 which accepts this as a newcommand signal.

The coded signal put out by generator 284 is the code for a particularcharacter location in the font unit which also represents the removalalignment position of the font unit as previously described. Althoughthis new command is seen" by the selector control 258 as a character tobe selected, the selection operation can not be initiated becausefunction decoder 260 has not been reset and hence cannot put out a Wsignal to start selection. However, after generator 284 has put out itscoded signal, set-up unit 280 puts out a combined start, print inhibit,and record signal. This signal goes out over lead 286 to OR gate 262 toeffect start of character selection to the font removal alignmentposition, to AND gate 268, and to print inhibit circuit 290. Printinhibit circuit 290 holds off any printing operation by print control268 until the system receives a reset pulse.

When character selection to the removal alignment position has beeneffected, selector control 258 puts out a normal C=P signal which isprevented from initiating a printing sequence by inhibit 290, but isalso presented to AND gate 288 which, inasmuch as a signal is alreadypresent on lead 286, now puts out a record signal to carriage positionmemory 292 and a run out signal to print carriage positioning controls272. Position memory 292 records the instant incremental position of thecarriage on receipt of this signal. The application of the run outsignal to controls 272 effects the start of high speed carriage movementto its limit stop position, as previously described for FIGS. 1 and 4,and also inhibits any margin or tabulation stopping of the carriageduring this travel. The high speed run out travel to the limit stop isterminated by a stop signal from limit switch 294. This run out of thecarriage removes the font unit from its drive means and positions it fortransfer to storage.

Position memory 292 is composed of appropriate switching and controlcircuits and a memory system which may be a code-controlled tabularmemory as disclosed in Cross-Ref. D. Memory 292 may also be composed ofa magnetic transducer and a magnetic recording drum as shown in FIG. 1and switched as shown in FIG. 7. Further, memory 292 can comprise anyone of the following: a pin cam mechanical memory; reversableoptochemical recording means; an up-down counter; an up'down shiftregister; or the like.

Assuming that memory 292 includes an up-down counter (to facilitateoperational function description), the presence or application of therecord signal readies the counter for operation. When carriagepositioning controls 272 responds to the run out signal, it operatesmotor 274, (nominally a stepping motor), by putting out a series ofincrementing pulses. When operating in the run out direction thesepulses are also applied to the memory 292 as up count pulses. When thecarriage is returned from the limit stop in response to a run backsignal, the incremental drive pulses are supplied to the memory as downcount pulses, and when the count returns to zero, the memory 292 putsout a stop pulse to controls 272. Depending upon the speed of carriagerun back, memory 272 may be arranged to put out the stop pulse one ormore counts before the count gets down to zero. This early stop pulseprovides time for the carriage to be slowed down and stopped withoutovershoot on the part of motor 274.

After the carriage run out has been completed and the carriage halted bythe previously mentioned stop signal from limit switch 294 the font unithas been removed from its driving means as earlier described for FIGS. 1and 4. The same stop signal from the limit switch is also presented totime delay 296 which, after a brief delay of several milliseconds toassure that the carriage has come to a complete rest at the limit stop,puts out a stow signal to font transfer control and drive 298. Drive 298may be a unit such as actuator 222 shown in FIG. 6. Drive 298 transfersthe font unit from its received position and stows it in the storagemagazine. Upon completion of the transfer, drive 298 puts out a selectsignal to font selection control and drive 300, which may be a unit suchas shown in FIG. 6 which has a selector 218. Selection control and drive300, in response to the select signal, moves the magazine to thelocation previously commanded and held for reference in the set-upmemory 282 and, when that location has been reached, drive 300 stops andputs out an un-stow signal to transfer control and drive 298. Drive 298then un-stows the selected font unit from the magazine and transfers itinto position for installing on the driving means.

When this un-stowing and transfering motion is completed, drive 298 putsout a run back signal to carriage positioning controls 272 to effectreturn of the carriage to the position recorded by memory 292.Installation of the font unit takes place during the first part of thecarriage return motion. When the motion of the carriage has beenterminated as a result of a stop signal from memory 292, positioningcontrols 272 puts out a reset pulse which resets the system includingset-up 280, decoder 260, register 256, and input control 250.

It should be noted that the control system of FIG. 7 can be simplifiedin the interests of economy by the deletion of the carriage positionmemory 292 and drives 298 and 300 can be actuated by specific commandsignals sent to the system. For further economy drives 298 and 300 canalso be eliminated and font unit transfer effected by manual operationas shown in FIG. 5, and font selection effected as shown in FIG. 4.

The system of FIG. 7 is also provided with a system power supplyindicated at 310.

FIG. 8 shows a block diagram similar to that of FIG. 7, but provides forthe use of separate command signals to initiate font changing and fontreturn after manual font selection and incorporates the control detailfor a recording memory which may be the magnetic type shown in FIG. I.This control system may be applied to a structure such as illustrated inFIGS. 4, 5, and 6 and is, of course, particularly applicable to thestructure of FIGS. 1, 2, and 3 wherein the font receiver or storagemeans is manually rotated to effect font unit selection.

The control system of FIG. 8 has a system power supply 340 and thefollowing means, similarly numbered and named as those in FIG. 7, whichperform the same functions as described for FIG. 7: input control 350,keyboard 352, external input sources 354, input command register 356,selection control 358, function decoder 360, OR gate 362, font drivemotor 366, shaft position encoder 364, print control 368, printing drive370, print carriage positioning controls 372, carriage motor 374,feedback commutator 376, and line feed controls and drive 378.

Character selection and printing and line feeding and carriagepositioning are similar to that described for FIG. 7. In the system ofFIG. 8 however, two input signals are required to effect certain fontchange operations. The first input command signal, which calls for afont change, is decoded by decoder 360 and sent to font change circuit380 which puts out a multi-purpose signal which serves as a start signalto selection control 358 to bring the font unit to removal alignmentorientation or position, as an inhibit signal to print inhibit circuit390 to hold off printing until font change has been effected, and as arecord signal to AND gate 382. In this system it is assumed that thecoded input command signal calling for a font change is coded in such amanner that except for a difference in higher order bits or bit, it isalso the code for the particular character which represents the fontunit removal alignment position, (assuming that the font unit doesindeed have to be aligned for removal in some printers the font unit mayhave a normal home position thus obviating the need for this alignmentprocedure). With this special font change coded command signal,non-printing function decoder and switch 360 sees the signal as anonprinting function and hence does not put out a NPF or start signal toselection control 358. In this type of operation the higher order bit,or bits as required, are not presented to control 358 by register 356.

When character selection has been completed to the special position, theC=P signal put out by control 358 goes to AND gate 382 which now, withthe other input from font change 380 being already present, puts out asignal which serves to set recording head switch 384 to its l positionto accept a write signal when it is presented. The signal from AND gate382 also serves to set margin and tabulation inhibit circuit 386 whichlatches up and puts out a continuous inhibit signal to positioningcontrols 372. At the same time, the signal from AND 382 further servesto initiate run out of the carriage by controls 372 as described forFIG. 7. As carriage motor 374 responds to the incrementing pulses fromcontrols 372, its feedback commutator 376 puts out what amounts to anincrement completed pulse back to controls 372 to effect presentation ofthe next incrementing pulse. These feedback pulses are also presented tocounter 388 which is arranged to put out a pulse after a given inputcount. In this case taken as three increments, so as to delay therecording of the carriage position at the time of initiation of fontchange by that number of increments so as to provide an early readout ofthe recorded position to provide stopping time for carriage motion whenit is returned to the recorded position.

The output pulse from counter 388 goes to the single shot circuit 394which then puts out a pulse of proper length to write amplifier 396which, in turn, puts out a recording signal through switch 384 totransducer or recording head 398 which records the pulse on a memorysuch as a magnetic drum as shown in FIG. I. The transducer or recordinghead 398 is nominally of the write, read, and erase type.

When the carriage reaches its limit of travel or a few increments priorthereto, it actuates limit switch 400. The output of switch 400 servesto effect stopping of carriage motion to the run out limit through ORgate 402 as shown. The output of switch 400 also goes to recording headswitch 384 to effect setting of switch 384 to its position 3 which isthe read position.

After the carriage has reached the run out limit position, the font unithas been removed from its driving means and the exchange of the justremoved font unit for a desired font unit is effected by manualoperation as previously described. When manual exchange has beeneffected, a font return key is depressed on the keyboard to initiate thereturn of the carriage to the previously recorded position so thatprinting can be resumed. Again, as previously described, the newlyselected font unit or element is installed on the driving means bymotion of the carriage. This latter action of installation by carriagemotion, or unit removal for that matter, would not be necessary if thefont element is manually or otherwise removed from its driving means.

When the print carriage has reached the limit stop as described, thecontrols 372 puts out a reset signal which conditions the input control350, register 356, and decoder 360 to receive a font restore signal fromthe keyboard 352. This restore or return signal is decoded by decoder360 and sent to font return circuit 404 which then puts out a run backsignal to positioning controls 372. This run back signal initiatescarriage return to the previously recorded position. As the carriage isincremented in the run back direction, the magnetic memory drum or othermemory means responds in synchronism. When head 308 reads out therecorded pulse, it puts out a signal through switch 384 to readamplifier 404 which then puts out a multi-purpose signal which serves toeffect stopping of carriage movement by controls 372. The signal passesthrough OR gate 402. This same output from read amplifier 404 also goesthrough a time delay 406 which delays the signal by a sufficient amountto assure that the carriage has been stopped, and is used to effectreset of margin and tabulation inhibit 386 and to effect setting of headswitch 384 to position 2. When head switch is in position 2, eraseamplifier 406 is connected to head 398. This erase signal is left on andpresent until the head switch is conditioned to pass a write pulse. Thesystem is reset by the output pulse from the controls 272. With the newfont in place, printing is resumed.

It should be noted in FIGS. 7 and 8 that other carriage positioningsignals such as space, tabulation, etc. are sent to the print carriagepositioning controls over respective leads or cables from the decoderand switcher to the positioning controls. The temporary tab positionrecording sub-system, including memory types and method of control asdescribed herein to record carriage position at the time of initiationof font changing can also be used for other tabulation applications.

Many variations in the controls and structures are possible withoutdeparting from the spirit of this invention. For example, the variousfont storage means shown all have a cavity or aperture of some type tohold the stored font element. The receiver shown in FIG. 1 could equallywell have been fitted with stub shafts for retaining removed font units.

In the control system of FIG. 8, where it is assumed that there are twokeys on the keyboard for font changing operations, there could easily beother keys for font selection designation and the printer and controlsystem fitted with a font selection motor, and further, additionalinterlocks could be provided.

Both FIGS. 1 and 4 show the use of a long, transverse font unit driveshaft which necessitates positioning the carriage or transporter ateither the left or right extreme of travel for font unit, element, orspool exchange. If the long shaft is dispensed with and either ahorizontal or vertical stub shaft driving arrangement is used, the homeposition of the carriage can be at any location where it is mechanicallyconvenient to place the exchange mechanisms. If the font unit changingmechanisms are manually operated, the right side location, when facingthe printer, is preferred in order to satisfy human engineeringrequirements.

Further, in the figures and description, it has been assumed that thefont unit character selection motion, that is, rotation, is either oneof always rotating in one direction to get from one character to thenext; or shortest distance, i.e. minor arc, rotation in either directionto get to the next selected character. This means that the font unit orelement has no home" position and therefore, rotational alignment orindexing is necessary before removal. If character selection is effectedby back-and-forth rotation about a home" position, as in some singleelement typewriters, this alignment procedure is generally unnecessary.

I claim:

1. In a printer for producing printing along a writing line on arecording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing and non-printing functionssuch as spacing, tabulation, line feeding the recording material, andthe like, the combination comprising:

a. character selection means having driving means for positioning aninstalled type font unit to bring a selected character into position forthe printing thereof; b. carriage means, movable parallel to saidwriting line and along the length thereof, for supporting a type fontunit in installed position in engagement with said driving means forcharacter selection and in position for printing and spacing; c.carriage positioning means for moving and incrementally positioning thecarriage means to printing positions along the writing line, and also toa limit of travel in one direction which is at least one positioningincrement beyond the end of the writing line whereat type font units canbe exchanged; and d. means for removing a type font unit from saidinstalled position for exchange with a second font unit, and forinstalling said second font unit in said installed position, said meanscomprising said carriage means which does said removing as it approachessaid limit of travel and, after said ex change, does said installing asit leaves said limit of travel, e. said last-named means furthercomprising l. means receiving a type font unit from the carriage meansas it approaches the limit of travel, and holding said font unit when itis disengaged,

2. means exchanging said font unit with a second font unit, and

3. means positioning said second font unit for engagement with thedriving means, and removal from said receiving and exchanging means bysaid carriage means as it leaves said limit of travel.

2. The combination of claim 1 further comprising a carriage positionmemory and signalling means, cooperative with said signal responsivemeans and with said carriage positioning means, for temporarilyrecording the instant incremental position of the carriage meanswhenever carriage movement to said limit of travel for font unitexchange is initiated, and, after an exchange has occurred and carriagemovement away from said limit of travel has been initiated, for puttingout a signal to effect stopping of the carriage means at said recordedposition.

3. The combination of claim 2 further comprising:

a. positionable storage means, generally adjacent said limit of travel,for receiving and holding a plurality of type font units including theinstalled font unit when it is removed from installed position;

b. means for stowing a just removed font unit in the storage means, andfor un-stowing a second font unit from the storage means; and,

c. type font unit selection means for positioning the storage meansafter said just removed font unit has been stowed therein to bring saidsecond font unit into position for the un-stowing and subsequentinstallation thereof.

4. The combination of claim 3 wherein the carriage means furthercomprises said means for stowing and un-stowing, whereby the carriagemeans stows a font unit in the storage means during the removingthereof, and, after the storage means has been positioned to bring asecond font unit into position for un-stowing, un-stows said second fontunit from the storage means during the installing thereof.

5. The combination of claim 3 wherein said means for stowing anun-stowing type font units comprises:

a. movable transfer means, cooperative with said carriage means and saidstorage means, and supported adjacent said limit of travel for:

l. receiving and supporting a type font unit as it is removed from saidinstalled position by the carriage means;

2. transferring said font unit from the carriage means to the storagemeans and stowing it therein; and, after the storage means has beenpositioned to bring a second font unit into unstowing position,

3. un-stowing said second font unit and transferring it to the carriagemeans for subsequent installation thereof; and,

b. actuating means connected to said transfer means for:

I. normally positioning the transfer means for said receiving;

2. moving the transfer means in one direction for said transferring andstowing; and, after said positioning of the storage means.

3. moving the transfer means in the opposite direction for saidun-stowing and transferring to the carriage means.

6. The combination of claim 3 wherein said signal responsive meansfurther comprises control means responsive to type font unit changingsignals for:

a. effecting positioning of an installed font unit to a pre-assignedcharacter position which represents the alignment position for theremoving thereof and the installing of a second font unit;

b. inhibiting printing of the preassigned character when said installedfont unit is so aligned for said removing; and,

c. initiating movement of the carriage means to said limit of travel forsaid removing.

7. In a printer for producing printing along a writing line on arecording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing, and non-printing functionssuch as spacing, tabulation, line feeding the recording material, andthe like, the combination comprising:

a. character selection means having driving means for positioning aninstalled type font unit to bring a selected character into position forthe printing thereof;

b. carriage means, movable parallel to said writing line and along thelength thereof, for supporting an installed type font unit in engagementwith said driving means for character selection and in position forprinting and spacing;

c. carriage positioning means for moving and incrementally positioningthe carriage means to printing positions along the writing line, andalso to a limit of travel in one direction which is at least onepositioning increment beyond the end of the writing line whereat typefont units can be exchanged;

d. means supported by the carriage means and means located adjacent saidlimit of travel and arranged for conjoint operation for successivelydisengaging and engaging type font units with the driving means; and,

e. receiving and exchanging means adjacent said limit of travel for:

1. receiving a type font unit from the carriage means as it approachessaid limit of travel;

2. holding said font unit when it is disengaged;

3. exchanging said font unit with a second font unit;

and,

4. positioning said second font unit for engagement with the drivingmeans, and removal from said receiving and exchanging means by saidcarriage means as it leaves said limit of travel.

8. In a printer for producing printing along a writing line on arecording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing, and non-printing functionssuch as spacing, tabulation, line feeding the recording material, andthe like, the combination comprising:

a. carriage means, movable parallel to said writing line and along thelength thereof, for supporting an installed type font unit inoperational position for character selection, printing, and spacing;

b. carriage positioning means for moving and incrementally positioningthe carriage means to printing positions along the writing line, and toa limit of travel in one direction whereat type font units can beexchanged;

e. type font unit changing means, generally adjacent said limit oftravel, for removing a type font unit from said operational position,for exchanging said font unit with a second font unit, and forinstalling said second font unit in said operational position; and,

d. carriage position memory and signalling means, cooperative with saidsignal responsive means and said carriage positioning means, fortemporarily recording the instant incremental position of the carriagemeans whenever carriage movement to said limit of travel for font unitchanging is initiated, and, after font unit changing has occured andcarriage movement away from said limit of travel has been initiated, forputting out a signal to effect stopping of the carriage means at saidtemporarily recorded position.

9. The combination of claim 8 wherein said carriage position memory andsignalling means comprises a magnetic recording and control means havinga magnetic recording medium and a cooperating electromagnetic transducermeans for temporarily recording, reading out, and then erasing a recordof said instant incremental position of the carriage means, and whereinsaid recording medium and said transducer means are supported forrelative motion therebetween and in synchronism with the positioning ofthe carriage means.

10. The combination of claim 8 wherein said carriage position memory andsignalling means comprises a reversible counting means for temporarilyrecording said instant position by counting in incremental synchronismwith the movement of the carriage means whenever it is moved to and fromsaid limit of travel, and wherein said stopping signal is put out when acounting sequence has returned to either the start of count, or to oneor more increments therebefore to provide an adequate time interval forstopping the carriage means at the exact position represented by thestart of count.

11. In a printer for producing printing along a writing line on arecording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing, and non-printing functionssuch as spacing, tubulation, line feeding the recording material, andthe like, the combination comprising:

a. character selection means having driving means for positioning aninstalled type font unit to bring a selected character into position forthe printing thereof;

b. carriage means, movable parallel to said writing line and along thelength thereof, for supporting a type font unit in installed position inengagement with said driving means for character selection and inposition for printing and spacing;

c. carriage positioning means for moving and incrementally positioningthe carriage means to printing positions along the writing line, and toa limit of travel in one direction whereat type font units can beexchanged;

d. type font unit changing means, generally adjacent said limit oftravel, for removing a type font unit from said installed position, forexchanging said font unit for a second font unit, and for installingsaid second font unit in said installed position; and,

e. control means, cooperative with said signal responsive means andresponsive to signals calling for type font unit changing, for:

l. effecting positioning of an installed type font unit to apre-assigned character position which represents the alignment positionfor the removing thereof and the installing of a second font unit;

2. inhibiting printing of the pre-assigned character when said installedfont unit is so aligned for said removing; and,

3. initiating movement of the carriage means to said limit of travel forsaid removing and subsequent operations of font unit exchange and saidinstalling of said second font unit.

1. In a printer for producing printing along a writing line on arecording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing and non-printing functionssuch as spacing, tabulation, line feeding the recording material, andthe like, the combination comprising: a. character selection meanshaving driving means for positioning an installed type font unit tobring a selected character into position for the printing thereof; b.carriage means, movable parallel to said writing line and along thelength thereof, for supporting a type font unit in installed position inengagement with said driving means for character selection and inposition for printing and spacing; c. carriage positioning means formoving and incrementally positioning the carriage means to printingpositions along the writing line, and also to a limit of travel in onedirection which is at least one positioning increment beyond the end ofthe writing line whereat type font units can be exchanged; and d. meansfor removing a type font unit from said installed position for exchangewith a second font unit, and for installing said second font unit insaid installed position, said means comprising said carriage means whichdoes said removing as it approaches said limit of travel and, after saidexchange, does said installing as it leaves said limit of travel, e.said last-named means further comprising
 1. means receiving a type fontunit from the carriage means as it approaches the limit of travel, andholding said font unit when it is disengaged,
 2. means exchanging saidfont unit with a second font unit, and
 3. means positioning said secondfont unit for engagement with the driving means, and removal from saidreceiving and exchanging means by said carriage means as it leaves saidlimit of travel.
 2. moving the transfer means in one direction for saidtransferring and stowing; and, after said positioning of the storagemeans.
 2. holding said font unit when it is disengaged;
 2. Thecombination of claim 1 further comprising a carriage position memory andsignalling means, cooperative with said signal responsive means and withsaid carriage positioning means, for temporarily recording the instantincremental position of the carriage means whenever carriage movement tosaid limit of travel for font unit exchange is initiated, and, after anexchange has occurred and carriage movement away from said limit oftravel has been initiated, for putting out a signal to effect stoppingof the carriage means at said recorded position.
 2. means exchangingsaid font unit with a second font unit, and
 2. transferring said fontunit from the carriage means to the storage means and stowing ittherein; and, after the storage means has been positioned to bring asecond font unit into un-stowing position,
 2. inhibiting printing of thepre-assigned character when said installed font unit is so aligned forsaid removing; and,
 3. un-stowing said second font unit and transferringit to the carriage means for subsequent installation thereof; and, b.actuating means connected to said transfer means for:
 3. meanspositioning said second font unit for engagement with the driving means,and removal from said receiving and exchanging means by said carriagemeans as it leaves said limit of travel.
 3. The combination of claim 2further comprising: a. positionable storage means, generally adjacentsaid limit of travel, for receiving and holding a plurality of type fontunits including the installed font unit when it is removed frominstalled position; b. means for stowing a just removed font unit in thestorage means, and for un-stowing a second font unit from the storagemeans; and, c. type font unit selection means for positioning thestorage means after said just removed font unit has been stowed thereinto bring said second font unit into position for the un-stowing andsubsequent installation thereof.
 3. moving the transfer means in theopposite direction for said un-stowing and transferring to the carriagemeans.
 3. initiating movement of the carriage means to said limit oftravel for said removing and subsequent operations of font unit exchangeand said installing of said second font unit.
 3. exchanging said fontunit with a second font unit; and,
 4. positioning said second font unitfor engagement with the driving means, and removal from said receivingand exchanging means by said carriage means as it leaves said limit oftravel.
 4. The combination of claim 3 wherein the carriage means furthercomprises said means for stowing and un-stowing, whereby the carriagemeans stows a font unit in the storage means during the removingthereof, and, after the storage means has been positioned to bring asecond font unit into position for un-stowing, un-stows said second fontunit from the storage means during the installing thereof.
 5. Thecombination of claim 3 wherein said means for stowing an un-stowing typefont units comprises: a. movable transfer means, cooperative with saidcarriage means and said storage means, and supported adjacent said limitof travel for:
 6. The combination of claim 3 wherein said signalresponsive means further comprises control means responsive to type fontunit changing signals for: a. effecting positioning of an installed fontunit to a pre-assigned character position which represents the alignmentposition for the removing thereof and the installing of a second fontunit; b. inhibiting printing of the pre-assigned character when saidinstalled font unit is so aligned for said removing; and, c. initiatingmovement of the carriage means to said limit of travel for saidremoving.
 7. In a printer for producing printing along a writing line ona recording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing, and non-printing functionssuch as spacing, tabulation, line feeding the recording material, andthe like, the combination comprising: a. character selection meanshaving driving means for positioning an installed type font unit tobring a selected character into position for the printing thereof; b.carriage means, movable parallel to said writing line and along thelength thereof, for supporting an installed type font unit in engagementwith said driving means for character selection and in position forprinting and spacing; c. carriage positioning means for moving andincrementally positioning the carriage means to printing positions alongthe writing line, and also to a limit of travel in one direction whichis at least one positioning increment beyond the end of the writing linewhereat type font units can be exchanged; d. means supported by thecarriage means and means located adjacent said limit of travel andarranged for conjoint operation for successively disengaging andengaging type font units with the driving means; and, e. receiving andexchanging means adjacent said limit of travel for:
 8. In a printer forproducing printing along a writing line on a recording material, and ofthe type having a changeable type font unit normally installed inoperational position therein which can be removed therefrom andexchanged with a second font unit having a different set of characters,and having signal responsive means for effecting and controllingcharacter selection, printing, and non-printing functions such asspacing, tabulation, line feeding the recording material, and the like,the combination comprising: a. carriage means, movable parallel to saidwriting line and along the length thereof, for supporting an installedtype font unit in operational position for character selection,printing, and spacing; b. carriage positioning means for moving andincrementally positioning the carriage means to printing positions alongthe writing line, and to a limit of travel in one direction whereat typefont units can be exchanged; e. type font unit changing means, generallyadjacent said limit of travel, for removing a type font unit from saidoperational position, for exchanging said font unit with a second fontunit, and for installing said second font unit in said operationalposition; and, d. carriage position memory and signalling means,cooperative with said signal responsive means and said carriagepositioning means, for temporarily recording the instant incrementalposition of the carriage means whenever carriage movement to said limitof travel for font unit changing is initiated, and, after font unitchanging has occured and carriage movement away from said limit oftravel has been initiated, for putting out a signal to effect stoppingof the carriage means at said temporarily recorded position.
 9. Thecombination of claim 8 wherein said carriage position memory andsignalling means comprises a magnetic recording and control means havinga magnetic recording Medium and a cooperating electro-magnetictransducer means for temporarily recording, reading out, and thenerasing a record of said instant incremental position of the carriagemeans, and wherein said recording medium and said transducer means aresupported for relative motion therebetween and in synchronism with thepositioning of the carriage means.
 10. The combination of claim 8wherein said carriage position memory and signalling means comprises areversible counting means for temporarily recording said instantposition by counting in incremental synchronism with the movement of thecarriage means whenever it is moved to and from said limit of travel,and wherein said stopping signal is put out when a counting sequence hasreturned to either the start of count, or to one or more incrementstherebefore to provide an adequate time interval for stopping thecarriage means at the exact position represented by the start of count.11. In a printer for producing printing along a writing line on arecording material, and of the type having a changeable type font unitnormally installed in operational position therein which can be removedtherefrom and exchanged with a second font unit having a different setof characters, and having signal responsive means for effecting andcontrolling character selection, printing, and non-printing functionssuch as spacing, tubulation, line feeding the recording material, andthe like, the combination comprising: a. character selection meanshaving driving means for positioning an installed type font unit tobring a selected character into position for the printing thereof; b.carriage means, movable parallel to said writing line and along thelength thereof, for supporting a type font unit in installed position inengagement with said driving means for character selection and inposition for printing and spacing; c. carriage positioning means formoving and incrementally positioning the carriage means to printingpositions along the writing line, and to a limit of travel in onedirection whereat type font units can be exchanged; d. type font unitchanging means, generally adjacent said limit of travel, for removing atype font unit from said installed position, for exchanging said fontunit for a second font unit, and for installing said second font unit insaid installed position; and, e. control means, cooperative with saidsignal responsive means and responsive to signals calling for type fontunit changing, for: